1. Field of the Invention:
This invention relates in general to a valve for an oil well drilling rig, and in particular to a kelly cock valve that is remotely actuatable.
2. Description of the Prior Art:
In rotary well drilling, a string of drill pipe is rotated while drilling fluid is pumped down the string. In the majority of the drilling rigs, the drill string is rotated by means of a kelly, which is a square section of pipe located at the upper end of the drill string. The kelly slides through a kelly bushing in the rotary table on the rig floor. In another type, the drill string is rotated by a drive system located in the derrick.
In both types of drilling rigs, there is a need for a kelly cock valve located at the upper end of the string. This valve is remotely actuated by the driller in the event that drilling mud starts blowing up the drill pipe. This could occur in the event that a high pressure zone is encountered.
The known kelly cock valves employ a tubular body mounted to the kelly or the uppermost section of pipe in the drill string. A ball valve is located in the body for opening and closing the drill pipe. Fluid pressure applied to an actuator causes the ball valve to open and close.
Some of the types use a fluid collector or swivel for transmitting pneumatic or hydraulic fluid from stationary lines to fluid pistons and cylinders in the body which rotate with the body. Others employ stationary fluid pistons and cylinders located above the rotating body. These include means for transmitting linear movement from the stationary actuator to the components of the valve.
While these systems are workable, improvements are desirable. Particularly desirable would be a kelly cock that would enable repair and maintenance on the valve without needing to break out the valve body from the kelly in each case. Also, a valve that is well balanced is desirable. If not well balanced, the rotating components tend to cause vibration.